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A Slurry Consolidation Method for Reconstitution of Triaxial Specimens
Wenhua Liu,Xiao-Wei Tang,Qing Yang 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.1
In this paper, a modified slurry consolidation approach to reconstitute triaxial specimens was developed within an experimental program to study the influence of drying-wetting on the cyclic behaviors of unsaturated soils. The uniformity of the reconstituted specimens was assessed by measuring the dry density, water content, grain size distribution and the soil water characteristic curve throughout the specimens. Additionally, the static and cyclic triaxial tests were performed to further verify the ability of this new slurry consolidation method for preparing identical specimens. All the test results report very small differences between specimens. The slurry consolidation approach presented herein can produce specimens with a high initial degree of saturation of about 96%, expediting the subsequent saturation process. Finally, the cyclic triaxial tests were conducted on the unsaturated soils to investigate the influence of drying-wetting on the cyclic behaviors of unsaturated soils. Drying-wetting has an irreversible influence on the cyclic behaviors of unsaturated soils. The cyclic strength is increased after drying-wetting.
Wenhua Zhang,Rong Xiang,Shuang Wu,Bo Yang,Yu Liu,Jun Zhu,Huaqiao Gui,Jianguo Liu,Liang Lu,Benli Yu 한국물리학회 2014 Current Applied Physics Vol.14 No.5
In this paper we present a novel method of gas leakage detection based on self-mixing interference with an extremely compact Er3þ eYb3þ codoped Distributed Bragg Reflector (EYDBR) fiber laser. According to the simulation and theoretical analysis of gas leakage of tank, we infer that the vibration frequency peak of tank caused by gas leakage increases with the internal pressure. In the experiment, the results agree with the theoretical prediction and the relevance of polynomial fitting about the spectrum peak of tank vibration and internal pressure is 0.99725. Thus, we can get the internal pressure of tank by measuring the vibration frequency peak of tank. Moreover, it has important significance in the prevention of the accident of flammable or explosive gas leakage.
Wenhua Liu,Guoqian Hong,Wugang Li,Yi Zhang,Yang Sun 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.5
Soft clay presents many problems in the construction of infrastructures, which can be well solved by using effective solidification materials and technologies. The carbonated reactive magnesia (CRM) comes to the fore for its superiority in energy-saving and high solidification efficiency. Nevertheless, research on the applicability of CRM in soft clay solidifying is limited. In the current study, two major factors, including initial moisture content (w0) and reactive MgO content (Cm), were examined by measuring the unconfined compressive strength (UCS), mass and volume variations, and moisture content variation of CRM-treated soft clay. The intrinsic mechanisms were discussed based on the mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and X-ray diffraction (XRD) tests. The findings reveal that carbonated specimens with low Cm (≤ 25%) or w0 (≤ 25%) suffer from severe volumetric expansion and cracks, which cause serious reductions in UCS, and the strength of these specimens can be even much lower than that of the uncarbonated ones. Specimens with high Cm and w0 acquire satisfactory strength by carbonation, and the highest UCS can exceed 4 MPa, indicating that the CRM is capable of solidifying soft clay. Water and MgO are both vital for the crystallization of hydrated magnesium carbonates (HMCs), and Cm is also beneficial for restricting volumetric expansion and reducing macropores; while proper w0 is required for the formation and evolution of HMCs, especially the nesquehonite.
Complete conversion of cellulose to water soluble substances by pretreatment with ionic liquids
Weina Liu,Weize Wu,Yucui Hou,Shuhang Ren,Wenhua Wang 한국화학공학회 2012 Korean Journal of Chemical Engineering Vol.29 No.10
Pretreatment of cellulose to water soluble substances (WSS) can enhance its efficient conversion in water solvent, such as ethanol fermentation. In this work, we found ionic liquid (IL), 1-methyl-3-methylimidazolium dimethylphosphate ([Mmim][DMP]), could convert efficiently cellulose to obtain WSS, and the product WSS and IL mixture could be separated by ethanol anti-solvent way. Effects of ILs, time, temperature and water on cellulose conversion were investigated. NMR, FTIR, XRD and SEM were employed to study the mechanism of cellulose conversion with ILs. The results indicate that [Mmim][DMP] has a greater ability to interact with cellulose than [Bmim][Cl] under the same conditions. Cellulose can be completely converted into WSS in [Mmim][DMP] under all the investigated temperatures from 140 to 160 oC. Increasing temperature is beneficial to the conversion rate of cellulose. But the presence of water can decrease the conversion rate of cellulose. During the treatment by [Mmim][DMP], the hydroxyls of cellulose can form hydrogen bonds with both anion and cation of [Mmim][DMP], and after the treatment the inter- and intramolecular hydrogen bonds of cellulose and the compact structure of cellulose are collapsed.
Vibration Analysis of EMS-Type Maglev Vehicles Traveling over a Long-Span Bridge with Double Lines
Wei Liu,Wenhua Guo 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.5
This paper establishes a detailed three-dimensional (3D) model to study the spatial vibration characteristics of two middle-low speed vehicles traveling along a long-span bridge with double lines. Here, two state-space equations for the left- and right-hand maglev vehicles are derived, considering the equations of motion of vehicles, governing equations of currents, linear feedback controls and state observers. By employing the conventional finite element method, the equation of motion for the variable cross-section continuous girder bridge with three spans is simulated. To solve these three coupled equations, this study adopted a new separated iterative approach based on the precise integration method and the Newmark-βmethod. The total virtual work conducted by the inertial loads, damping loads, elastic loads and fluctuating electromagnetic loads are calculated to conveniently assemble the global mass matrix, damping matrix, stiffness matrix and coefficient matrices of fluctuating electromagnetic forces in the maglev vehicles. The numerical studies indicate that the vertical interactions play dominant roles in the 3D maglev vehicles-bridge system, and the passing maglev vehicles on the bridge have little influence on the lateral motions of the vehicle on the other line due to the adequate lateral stiffness of the bridge.
Hybrid phase-shifted modulation method for hybrid cascaded H-bridge inverters
Hu, Wenhua,Guo, Jiamin,Liu, Jianfeng,Yuan, Yisheng The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.10
Due to its unreasonable DC voltage distribution, the phase-shifted pulse width modulation (PS-PWM) method cannot be directly applied to equal-ratio and equal-difference hybrid CHB inverters. Thus, these types of inverters lose the double-frequency characteristic of the CHB topology. To preserve this double-frequency characteristic, reduce the switching frequency of the high-voltage cells, and simplify the modulation method. This article proposes an optimized topology for the hybrid CHB inverter by optimizing the distribution of the DC voltage. A hybrid PS-PWM method is also proposed by combing the step-wave modulation method and the PS-PWM method. Theoretical analysis, simulation analysis, and experimental results show that the optimized topology and the hybrid PS-PWM method are both valid and feasible.
Hui Li,Wenhua Xu,Xuying Liu,Junli Ye,Peijie Li,Fangfang Shang,Xiaoling Yu 한국식품영양과학회 2020 Journal of medicinal food Vol.23 No.9
Cisplatin is a widely used anticancer drug that has adverse effects on gastrointestinal function. Curcumin is a natural polyphenol extracted from the rhizome of turmeric that has a wide range of biological activities. The present study investigated the effects of cisplatin on gastric emptying in mice and examined whether these can be inhibited by curcumin. We found that pretreatment with curcumin (200 mg/kg/day) for 10–30 days partly inhibited the decreases in gastric emptying rate and body weight induced by cisplatin. Furthermore, cisplatin reduced acetylcholine (ACh) concentration and the messenger RNA (mRNA) level of ACh receptor (AChR) as well as acetylcholinesterase activity in the stomach of mice; caused ultrastructural damage to interstitial cells of Cajal (ICC); and altered the expression of c-kit/stem cell factor and the gap junction protein connexin 43 in ICC. Curcumin pretreatment inhibited the effects of cisplatin on ACh indicators and ICC. These results demonstrate that curcumin can protect against cisplatin-induced gastric emptying disorder and thus has therapeutic potential for alleviating this condition in cancer patients receiving cisplatin chemotherapy.